In horizontal axis wind turbines, the blades are typically relatively long, e.g., 20-40 meters in length. Generally, most horizontal axis wind turbines include either two or three blades. In general, the weight of the blades is a constraining factor in wind turbine design, and different materials and methods of construction are known which are intended to provide blades which are sufficiently strong to withstand the stresses to which they are subjected, but have minimal weight.
In the prior art, various fibreglass composite fabrication techniques typically are used to make the known wind turbine blades. These techniques typically involve manual labor, i.e., they are relatively costly, and there may be some quality control issues. Typically, the entire blade is formed in one piece.
Another disadvantage of the known wind turbine blades is the cost of constructing a wind turbine using such blades. Typically, each prior art blade is formed as an integral unit respectively, and each blade must be transported to the site at which the turbine is to be assembled. In some cases, however, it is not possible to construct a wind turbine in an advantageous location because of the difficulties involved in transporting the fully-formed blades to the site. In addition, due to the large size of each blade, the assembly of known wind turbines tends to be relatively expensive.
Also, if a prior art single-piece blade is damaged (e.g., during assembly or operation), then the entire blade usually must be replaced. This involves significant costs.